1. Field of the Invention
The present invention pertains to the field of x-ray machine positioning systems. Specifically, the present invention relates to the use of a laser aiming system with a C-arm x-ray machine.
2. Prior Art
Laser light beams have been used in prior art systems for positioning various types of equipment. One such positioning system is disclosed in U.S. Pat. No. 5,031,203, titled Co-axial Laser Targeting Device For Use With X-ray Equipment And Surgical Drill Equipment During Surgical Procedures, invented by Randal R. Trecha (hereinafter denoted the '203 Patent). The '203 Patent discloses an apparatus including a laser light emitting means (laser source) disposed on an x-ray gun portion for emitting a beam of visible laser light. This apparatus includes a target grid means disposed on the x-ray collector portion for targeting the visible laser light in co-axial relationship with the longitudinal axis of the x-ray radiation between the gun portion and the collector portion of the x-ray equipment. The apparatus described in the '203 Patent further includes a radiolucent plastic mirror assembly mounted on the laser emitter. The central ray of the x-ray shares the path of the laser as it is reflected off the mirror, so that the x-ray and the laser are co-axial with one another. The apparatus described in the '203 Patent is useful for locating interlocking screw holes in intramedullary rods, placement of pedicle screws in spinal surgery, placement of wires for percutaneous and open fixation, accurate positioning of the image intensifier without exposure to radiation, and accurate percutaneous pin placement of an external fixation in pelvic fractures.
The apparatus described in the '203 Patent has several disadvantages. First, the configuration described in the '203 Patent requires that the x-ray emitter and the laser source be positioned above the level of a table upon which a patient or subject is situated. If this were not the case, the table would shield the laser beam and render the targeting apparatus unusable. In actual practice, x-ray emitters are often positioned below the level upon which patients or subjects are situated. In fact, C-arm mounting supports are well known and used in prior art x-ray systems for the purpose of positioning an x-ray emitter in any arbitrary position about a subject under examination or surgical operation including below table level. The configuration of the apparatus described in the '203 Patent substantially limits the utility of the C-arm support structure.
A second disadvantage of the apparatus described in the '203 Patent again pertains to the fact that the laser source is disposed on the x-ray emitter or x-ray gun portion of the x-ray device. In this configuration, the x-ray emitter must always be positioned above the level of the table upon which a patient or subject is situated. When the x-ray emitter is positioned in this manner, the operating room staff is fully exposed to scatter radiation emitted from the primary x-ray beam and to non-attenuated x-ray beam radiation from the x-ray emitter. When the x-ray emitter is positioned below the level of the table, the patient and the patient table absorb much of the scatter radiation, and attenuate the x-ray beam. This reduces radiation to the operating room staff, particularly radiation to the staff's hands, faces, and eyes. Thus, although the apparatus described in the '203 Patent may provide a co-axial laser targeting device, significant problems in the practical application of the device limit the utility of the apparatus.
Other laser targeting systems for x-ray machines are available from Gammex, Inc. of Milwaukee, Wis. The Gammex laser systems use two laser sources disposed on the x-ray emitter that together form a visible crosshair of light that defines the center ray of the x-ray emitter. The Gammex system is similar to the apparatus described in the '203 Patent in that the laser source is disposed on the x-ray emitter; however, the Gammex laser system does not emit a point laser co-axial with the center beam of the x-ray emitter. Rather, the Gammex laser targeting system comprises two laser sources. One laser source emits a fan laser beam in a generally horizontal direction, while the other laser emitter emits a fan beam generally oriented in a vertical direction. The two fan laser beams are calibrated to cross at a point corresponding to a position on the center beam of the x-ray emitter. Because the Gammex system comprises two laser sources, the laser targeting system is more difficult to calibrate with the x-ray emitter.
U.S. Pat. No. 4,442,533 discloses an indicator for visibly defining the image plane located at the moveable fulcrum of a tomography x-ray machine. The indicator includes a laser beam light source mounted for vertical movement along a rack and pinion assembly. This indicator does not provide an indication of the longitudinal axis of the central x-ray beam as would be required when making transverse bores in a patient's bone in register with the bores of an osteosynthesis aid in the bone.
U.S. Pat. No. 4,426,726 discloses an apparatus and method for aligning the center of an x-ray beam with both a reference point on a patient and the center of the x-ray film holder. A visible light source is disposed on an x-ray emitter in a manner similar to the '203 Patent. The visible light source emits two fan beams which provide two fan beam planes. The fan beam planes perpendicularly bisect the x-ray beam and each other to form a line of intersection corresponding to the center of the x-ray beam. In a manner similar to the Gammex laser devices, the two visible light sources emit fan beams that may be calibrated to correspond to the center beam of the x-ray emitter. Again, however, the visible light source is not co-axial with the center beam of the x-ray emitter. Moreover, because the device has two visible light sources, the apparatus is more difficult to calibrate.
The light beam producing device described in U.S. Pat. No. 4,337,502 also describes an apparatus for producing vertical and horizontal planes of visible light. The intersection of the light planes with the body of the subject under examination forms luminous lines that may be used to properly orient the patient with respect to the light lines.
Laser light beams have also been used to calibrate tomography machines using phantoms as disclosed in U.S. Pat. No. 4,296,329, and for calibrating linear accelerators, or a cobalt-60 teletherapy machine as is disclosed in U.S. Pat. Nos. 4,123,660 and 4,223,227.
U.S. Pat. No. 4,625,718 discloses an aiming apparatus for making transverse bores in a patient's bone in register with the holes or bores of an osteosynthesis aid in the bone. This apparatus includes an aiming member adapted to be brought into the beam path of an x-ray device. This apparatus is difficult to use and typically not as accurate as a laser targeting device.
Thus, a better means is needed for aiming an x-ray emitter with a laser aiming device.